Change parallax scrollx to float factor

assets/levels/R2/parallax.toml

@@ -3,7 +3,7 @@ width = 256
 height = 44
 u0 = 0
 v0 = 0
-scrollx = 0 # TODO
+scrollx = 0.0 # TODO
 y0 = 64
 single = false
 

include/parallax.h

@@ -35,7 +35,7 @@ typedef struct {
 typedef struct {
     uint8_t num_parts;
     uint8_t is_single;
-    int16_t scrollx;
+    int32_t scrollx;
     int16_t y0;
     uint16_t width; // Sum of all widths, calculated on load!
     ParallaxPart *parts;

src/parallax.c

@@ -33,7 +33,7 @@ load_parallax(Parallax *parallax, const char *filename)
 
         strip->num_parts = get_byte(bytes, &b);
         strip->is_single = get_byte(bytes, &b);
-        strip->scrollx   = get_short_be(bytes, &b);
+        strip->scrollx   = get_long_be(bytes, &b);
         strip->y0        = get_short_be(bytes, &b);
 
         strip->parts = alloc_arena_malloc(

tools/buildprl/buildprl.py

@@ -12,6 +12,14 @@ c_ushort = c_ushort.__ctype_be__
 c_int = c_int.__ctype_be__
 
 
+def tofixed(value: float, scale: int) -> int:
+    return int(value * (1 << scale))
+
+
+def tofixed12(value: float) -> int:
+    return tofixed(value, 12)
+
+
 @dataclass
 class ParallaxPart:
     u0: int = 0
@@ -31,14 +39,14 @@ class ParallaxPart:
 @dataclass
 class ParallaxStrip:
     single: bool = False
-    scrollx: int = 0
+    scrollx: float = 0
     y0: int = 0
     parts: [ParallaxPart] = field(default_factory=list)
 
     def write_to(self, f):
         f.write(c_ubyte(len(self.parts)))
         f.write(c_ubyte(int(self.single)))
-        f.write(c_short(self.scrollx))
+        f.write(c_int(tofixed12(self.scrollx)))
         f.write(c_short(self.y0))
         for p in self.parts:
             p.write_to(f)

tools/layouts/prl.hexpat

@@ -11,7 +11,7 @@ struct ParallaxPart {
 struct ParallaxStrip {
        u8 num_parts;
        u8 is_single;
-       be s16 scrollx;
+       be s32 scrollx;
        be s16 y0;
        ParallaxPart parts[num_parts];
 };